Tuesday, October 25, 2011

One of the Navy's ongoing concerns is defense of its ships from attacks by aircraft and/or missiles. The Chinese anti-ship missile threat is only the latest. In the 1950s, it was long-range, high-performance missiles launched from Soviet bombers. The first solution was the Sparrow air-to-air missile carried by fighters whose development had begun in the late 1940s. The F4H Phantom was the first Navy fighter specifically designed for the mission and was also armed with the Sparrow. However, the Navy continued to fret about a combination of faster bombers and longer range air-to-surface missiles that the Phantom/Sparrow approach was not capable of adequately addressing.

The solution from operational analyses was the Missileer concept. The Operational Requirement was issued on 11 July 1955. The "fighter" would simply be a subsonic platform that loitered out on a station on the threat axis, lugging a huge, long-range radar and up to eight very long-range air-to-air missiles. The missile's range requirement necessitated that it be provided with its own radar for terminal guidance. That and fuel required range that it was a very big missile indeed. It was to be called Eagle.

Work on the missile and engine design definition began first, because they would take much more time to develop and qualify than the airframe. The Bendix Corporation was selected as the prime contractor for the Eagle, including the airborne radar and missile control system, in December 1958. Grumman (airframe and flight test), Westinghouse (aircraft radar), Litton (tactical computer), Sanders (missile active pulse doppler seeker), and Aerojet (propulsion) were subcontractors.

The missile with its booster was 16-feet long. Together, they weighed 1,288 lbs, including the missile's on-board radar and 110-lb warhead. The maximum range from launch to intercept was 100 nautical miles against a bomber flying at 60,000 feet and Mach 2.

The Pratt & Whitney TF30 engine was one of the first turbofan-type engines, desired for its benefit on endurance. It was based on an engine that Pratt was developing for airlines.

The invitation to bid on the aircraft wasn't requested until 11 December 1959. Bids were received at the end of February from Chance Vought, Douglas, Grumman, McDonnell, and North America. Douglas was selected. The decision was announced on 21 July 1960.

The Navy's press release was explicit about the F6D's role: "The EAGLE-MISSILEER weapon system employs the concept of building long range and high performance into the missile, rather than into the launching aircraft." The 50,000-lb takeoff-gross-weight airplane was to be capable of operating from Essex-class carriers and loiter on station for four hours at 35,000 feet.

The bulbous nose was necessary to accommodate the Westinghouse AN/APQ-81 radar dish, which was five feet in diameter. (Big as the radar was, the missile's maximum range could only be utilized with the Bendix home-on-jam option.) The two-man crew sat side-by-side, surrounded by avionics. The normal missile load was six, all carried under the wings. Two additional missiles could be carried under the fuselage, increasing the takeoff gross weight by 4,800 lbs.

Unfortunately, the incoming Secretary of Defense, Robert McNamara, decided that it would be cost effective to combine two nascent "fighter" programs, the Navy's carrier-based, subsonic, 35,000-ft loiter Missileer and the Air Force's land-based, supersonic, tree-top ingress, nuclear-strike TFX. Strictly speaking, neither was a fighter and what's worse, two more different tactical airplane requirements would be difficult to imagine. The F6D program was formally terminated in April 1961 (it had been on hold since December 1960 awaiting the Kennedy administration's DoD programs review); Hughes took over the development of the radar/missile program, which was appropriately renamed Phoenix.

The F-111 train wreck, particularly given the Navy's outrage at being subservient to Air Force program management and subsequent passive-aggressive cooperation, was inevitable. For more on the F-111B program history, buy my F-111B monograph HERE.

Saturday, October 15, 2011

The Grumman WF-2 (E-1B) is an interesting example of the Navy designation system and a little known false start for an iconic Navy airplane, the "Stoof with a roof". For starters, what was the WF-1? And why is there no E-1A?

The basic designation was W for Airborne Early Warning (AEW) and F for Grumman. Up until then, W was a suffix, not a prime mission designation, as in TBM-3W. It indicated that an existing airplane type, the third modification (3) of the first Torpedo Bomber (TB) to be built by Eastern Aircraft (M), had been modified for the AEW mission (W) by substituting a large radar and its cover for the bomb bay. (The 3 actually reflected that it was the third modification of the TBF, since the airplane was originally designed, developed, and produced by Grumman as its first torpedo bomber, with Eastern Aircraft, a division of General Motors, taking over its production from Grumman.)

The TBF-3W was followed by a series of AD Skyraiders, like the AD-3W shown here, modified similarly to carry the APS-20 radar aloft.

As an aside, the similarly configured Grumman AF-2W was used for AntiSubmarine Warfare (ASW), not AEW, with the radar being used to detect a surfaced submarine or more likely, its snorkel. It was paired as a hunter with the AF-2S, the killer half of an ASW team, which was equipped and armed to localize and sink the submarine.

Grumman was in the process of replacing the AF-2W and AF-2S with the S2F, a twin-engine airplane that combined the mission equipment and armament of those two airplanes into one. The S for ASW was now a prefix as W would be for AEW.

The S2F's small radar that was housed in a retractable "dustbin" dome under the aft fuselage was optimized for surface surveillance, not AEW. Grumman therefore proposed a minimally modified S2F airframe for the AEW role, with the APS-20 radar and dome mounted above the cockpit rather than under the fuselage, which would have required a much longer landing gear and therefore required a folding vertical fin/rudder to meet the hangar-height limitation. The forward location of the radome meant that the existing S2F wing-fold system that overlapped the fuselage could be retained. The only change required to the airframe therefore was a slightly deeper fuselage with an aft cabin door and the addition of finlets to the horizontal stabilizer to compensate for the sail area forward that was added by the radar dome.

The Navy ordered two prototypes as the WF-1 and assigned them BuNos 133043 and 133044. Grumman accomplished wind tunnel tests and a fuselage mockup before the WF-1 effort was terminated, probably due to budget priorities and the availability of the AD-5W.

Vought got a contract for the WU-1 and two Bureau Numbers were assigned, 133780/1, but it was also cancelled. (Note the wing-fold arrangement used to accommodate the radar dome.)

Eventually, however, the Navy felt the need to use a bigger, better radar for the AEW mission. The existence of and commonality with the TF-1 Carrier on Board Delivery (COD) variant of the S2F, which had been proposed at the same time as the WF-1, was no doubt one of the deciding factors in the decision to award the program to Grumman.

The resulting WF-2 bore only a family resemblance to the S2F and TF, however. The radar was now mounted above the fuselage, which required the substitution of an H-tail and a reversion to the sto-wing fold system that was a Grumman invention. The capacious TF-1 fuselage was lengthened ahead of the wing, probably to maintain the required center of gravity. Because of uncertainty about the aerodynamic implications of the huge radome, TF BuNo 136792 was modified, except for the fuselage extension and sto-wing, for initial flight test with the radome. (Note the feathered engine.)

In the following picture, the aerodynamic prototype is flying in formation with a production WF-2. Note the different location of the propeller strip versus the pilot's side window, which indicates where the forward fuselage was extended forward.

The sto-wing necessitated the use of a free-swiveling tail wheel because of the aft shift in the center of gravity when the wings were folded.

I can't confirm that the prototype was designated the XTF-1W as Wikipedia currently states. It doesn't seem likely and Larry Webster confirmed that its history card only states TF-1 and C-1A. A very early (but not dated) Grumman S2F brochure describes the AEW and the COD versions as the WF-1and TF-1 respectively. I've also read that the aerodynamic prototype was designated WF-1, with the production airplane therefore being the WF-2. That's definitely bogus.

After Grumman flight test of the aerodynamic prototype, the radome was removed, the TF/C-1 interior installed, and the aircraft utilized as a transport by NAS Quonset Point, RI.

According to Angelo Romano, there were three other topless Tracers that were used for pilot training since field carrier landings and real carrier landings, not to mention catapult launches, were hard on the electronics, not to mention that the radar and guys in back were unnecessary for that requirement.

When Navy aircraft designations were changed in 1962 to be consistent with the Air Force system, the WF-2 became the E-1B. Although it could have been argued that there was no need to reflect a universe in which the WF-1 had not been cancelled, the group in charge of redesignation chose to do so.

Wednesday, October 5, 2011

Captain Carballo and noted Argentinian artist and illustrator Carlos A. Garcia provided more material and Carballo's copilot's name for my post on the one disappointing reproduction in Scooter!. For the update, go to http://thanlont.blogspot.com/2011/09/scooter.html

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In 1956, at age 12, I lived on NAS Sangley Point in the Philippine Islands. Always enamored with airplanes, I imprinted on the Cougars, Banshees, and Skyraiders then being deployed. Not able to be a Naval Aviator because I was nearsighted, I instead became an aeronautical engineer and general aviation pilot. Now retired, I write books and monographs on U.S. Navy aircraft.